Document a17D1jGDjE0xa4b9pxZajmvQb

American Society of Heating and Ventilating Engineers Guide, 1932 for brick walls are more probably representative of poor workmanship with porous brick and lime mortar. For good workmanship, the leakage through hard brick walls with cement-lime mortar does not exceed onethird the values given. These tests indicate that plastering reduces the leakage by about 96 per cent; a heavy coat of cold water paint, 50 per cent; and 3 coats of oil paint carefully applied, 28 per cent. The infil tration through walls ranges from 6 to 25 per cent of that through windows and doors in a 10-story office building, with imperfect sealing of plaster at the baseboards of the rooms. With perfect sealing the range is from Table 1. Infiltration through Walls Expressed in cubic feci per square foot per hour* Ttpb op Waul Wind Vblocitt. Miles per Hour ' 5 10 IS 20 25 30 8^in. Brick Wall...... 1.75 4.20 7.85 12.2 18.6 22.9 0.017 0.037 0.066 0.107 0.161 0.236 13 in. Brick Walt........ 1.44 3.92 7.48 11.6 16.3 21.2 0.005 0.013 0.025 0.043 0.067 0.097 Frame Wall, with lath and plasterb 0.03 0^07 0.13 0.18 0.23 0.26 Frame Wall, with lath and piaster^ 0.02 0.05 0.10 0.15 0.20 0.25 oThe values in this table are 20 per cent less than test values to allow for building up of pressure in rooms. bWall construction: Bevel siding painted. No. 1 common butt-edged sheathing, building paper, wood lath and 3 coats gypsum plaster. cWall construction: Cedar shingle, shiplap sheathing, building {taper, wood lath and 3 coats gypsum plaster. 0.5 to 2.7 per cent or a practically negligible quantity, which indicates the importance of good workmanship in proper sealing at the baseboard. It will be noted from Table 1, that the infiltration through properly plastered walls can be neglected. The value of building paper when applied between sheathing and. shingles is indicated by Fig. 1, which represents the effect on outside construction only without lath and plaster. The effectiveness of plaster properly applied is no justification for the use of low grade building paper or of the poor construction of the wall containing it. Not only is it difficult to secure and maintain the full effectiveness of the plaster but also it is highly desirable to have two points of high resistance to air flow with an air space between them. The amount of infiltration that may be expected through simple walls used in farm and other shelter buildings, is shown in Fig. 2. The infil tration there indicated is that determined in the laboratory and should be. multiplied by the factor 0.80 to give proper working values. 72 Chapter 4--Air Leakage from Buildings Fig. 1. Infiltration through Various Types of Shingle Construction INFILTRATION THROUGH WINDOWS The amount of infiltration in cubic feet per hour per foot of crack for various types of windows is given in Table 2. The distinction between crack and clearance of a wood sash is shown by Fig. 3. For window and sash leakage, the length of crack in double-hung windows is equal to the perimeter of sash plus length of meeting rail. For steel sash the length of crack is the aggregate perimeter of the movable or ventilating sections Fig. 2. Infiltration through Single Surface Walls Used in Farm and Other Shelter Buildings 73